Modal verbs

Modal verbs are a small set of helping verbs that change the meaning of the main verb rather than describing an action themselves. The core modals are can, could, may, might, must, shall, should, will, and would. Each adds a shade of meaning: ability (she can swim), permission (you may leave), possibility (it might rain), obligation (you must sign), advice (you should rest), or future intention (they will arrive).

Modals follow strict grammatical rules. They never change form — no -s for third person (he can, never he cans), no -ed, no -ing. They are always followed by the base form of the main verb: she might go, not she might goes or she might going. To express past or perfect meaning, modals pair with have plus a past participle: she should have called, they must have left.

Choosing the right modal is often a matter of degree. Must expresses stronger obligation than should; will expresses more certainty than might. Formal writing also distinguishes may (permission) from can (ability), and could and would soften requests: could you help me is more polite than can you help me.

The Praxis Core Writing exam tests modal verbs alongside perfect tenses. Expect questions on modal-plus-base-form construction, the modal + have + past participle pattern, and error-spotting items where a conjugated verb incorrectly follows a modal.